I. Field of the Invention
This invention relates generally to a releasable fastening device used for holding several workpieces together, and more specifically, to an improved releasable fastener sometimes referred to as a "blind fastener" that is capable of holding several workpieces together in a firm and intimate relationship and that can also compensate for a tolerance buildup between the workpieces.
II. Description of the Prior Art
The releasable fastener described herein is sometimes referred to as a "blind fastener". This type of fastener is primarily intended to be used with a workpiece or support member, such as a wall or any other type of sheet material, in mounting one or more items to the workpiece through the use of an elongated member, such as a bolt or screw. Thus, for example, a blind fastener can be used in mounting a picture upon a wall or in securing two or more workpieces or support members together. These fasteners are often employed in situations involving the mounting of fixtures or structural elements on support members, such as walls, in those situations in which it is very difficult or impossible to secure the fastener to the rear or blind side of the support member.
While many different kinds of these fasteners are used commercially, they do have many disadvantages. For example, many such devices typically must be formed of certain light gage materials which will allow the device to undergo a certain amount of deformation when used. Many require the use of a great deal of force to install the device. In addition many of these devices are limited in use in that they can only be employed with workpieces having a particular thickness.
Certain of the prior art blind nut or anchor bolt assemblies are multi-piece devices which are very complex in structure and very expensive due to the relatively high manufacturing costs of the device. Furthermore, these prior art type of anchor bolt devices generally require one to make excessively large holes in the workpieces which are to be assembled together. They have the additional disadvantage that the screws used with the fastening device cannot be removed after installation without the toggle portion being disengaged from the rear surface and generally lost. In such cases, the device must be replaced.
When one is examining the various blind fasteners that are described in the prior art and is making an attempt to improve on such devices, it is important to consider that such an improved fastener should be made comparatively inexpensive in order to be commercially acceptable. However, it is also necessary that any such fastener be relatively simple to use. In addition, while considering these factors, it is also very important that the fastener be constructed so as to provide a strong holding force to secure workpieces together in a firm and intimate manner.
Examples of some other types of fasteners related to the type of releasable fastener described by the present invention can be found in U.S. Pat. Nos. 1,179,9597, 1,755,590, 2,132,284, 2,826,231, 2,948,317, 3,091,030, 3,126,835, U.S.S.R. Pat. No. 868,149 and Belgium Pat. No. 508,342.